3-Ethylphenol is produced by sulfonation of ethylbenzene and subsequent alkali melt of the 3-ethylbenzenesulfonic acid obtained. By sulfonation under severe (thermodynamically controlled) conditions (200 ℃) the 4-ethylbenzenesulfonic acid formed initially isomerizes to form a mixture of 2-, 3-, and 4- ethylbenzenesulfonic acids in a ratio of ca. 2 : 58 : 40. The 2- and 4-ethylbenzenesulfonic acids are selectively hydrolyzed back to ethylbenzene and H2SO4 by blowing steam through the mixture at 150–170 ℃. 3-Ethylphenol is then obtained by alkali melt of the remaining 3-ethylbenzenesulfonic acid at 330–340 ℃ in up to 98% purity.
